AGIL
ACTIVE GLUCOSE INSULIN
CONTROL SYSTEM
Diabetes affects more than 177 million people worldwide, leaving those affected dependent on external methods of controlling the amount of glucose in their blood. Maintaining an acceptable level of blood glucose is essential for both short-term and long-term health. If levels become too high, a condition called hyperglycemia, the individual may become light-headed and feel ill. If levels become too low, called hypoglycemia, the individual may suffer from a lack of alertness, or even lose consciousness. In the long term, however, the consequences of greatly fluctuating blood glucose levels are even more serious, including damage to the nervous system, heart, and kidneys.
However, when blood sugar levels are kept within an acceptable range, these negative effects can be greatly ameliorated or even avoided altogether. Studies show a strong correlation between poor blood glucose management and these negative side effects; but the opposite is true as well. Essentially, the more blood glucose levels stay within a healthy range, the smaller the chance of negative side effects becomes. There are many factors that influence glucose levels in the human body, including diet, exercise, and sleep. The key to effective diabetes care, then, is to provide the means to a lifestyle that allows all these factors to be kept under control, and where treatment methods are as unobtrusive as possible.
In people without diabetes, glucose levels are controlled by the pancreas, through the production of a chemical called insulin. Insulin allows the body’s cells to absorb glucose from the bloodstream, keeping the cells nourished and regulating the level of glucose in the bloodstream. In people with diabetes, the pancreas does not produce the proper amount of insulin needed to keep glucose levels within the proper range. Without insulin production, glucose accumulates in the bloodstream to dangerous levels, and cells cannot get the energy they need to function properly. Thus, many require some form of supplementary insulin delivery.
While treatment plans for diabetes vary from one individual to the next, there are three types of diabetes that require different treatment. The first is type 1 diabetes, which was formerly known as juvenile diabetes. While it accounts for only about 5-10% of known diabetes cases within the United States, individuals with type 1 diabetes are the most likely to require constant glucose monitoring and to be dependant on insulin injections, and so are the most likely users of our system. This is because type 1 diabetes is caused by an (total) inability to produce insulin. Since all insulin in the body must then be delivered, the responsibility rests on the individual to do the job their body’s job. Individuals with type 1 diabetes must monitor their diets closely, and respond appropriately to actions that affect blood glucose levels.
Type 2 diabetes is much more common than type 1 diabetes, accounting for 90-95% of known diabetes cases within the United States. It occurs when insulin production is insufficient, or when the body’s cells develop a resistance to insulin. Since some cases of type 2 diabetes can be managed through diet control, exercise, and some medications, a lower percentage of type 2 diabetics will need our system.
Gestational diabetes is a condition developed during pregnancy where the mother is not able to produce enough insulin to accommodate for the changing needs of her body. It affects approximately 4% of pregnant women. Gestational diabetes is dangerous to both the mother and the unborn infant, as high glucose levels can also affect the growth of the fetus through its sensitive and critical maturation. Gestational diabetes requires careful monitoring of glucose levels and insulin delivery, so mothers with this condition can benefit from using our system.
Effective diabetes treatment is multi-faceted, often including a regulated diet, regular exercise, and an avoidance of harmful habits such as drinking and smoking, in addition to blood sugar monitoring and insulin delivery. However, our system focuses on the delivery of insulin and the monitoring of blood glucose levels.
Two fundamental types of insulin dosing are employed in the treatment of diabetes: a dose of fast-acting insulin, called a bolus, and discrete or continuous doses of slower-acting insulin. The bolus is delivered to offset an action that would raise blood sugar levels quickly, usually eating a meal. Its effects are visible quickly, and the timing of the delivery is important. There are two methods of controlling blood sugar over a longer period of time. The first is a single large dose of insulin that acts slowly over time, such as Lantus. The second is through a continuous delivery of insulin in small quantities, at a rate called the basal rate.
There are many methods currently available to deliver insulin. Perhaps the most common and traditional is through injections. This method is simple, and allows the user to be in full control of how much insulin they deliver and when. The main disadvantage is that all insulin deliveries are discrete events, and continuous or near-continuous insulin delivery is not possible. Its effects can be simulated with insulin that acts slowly over time, such as the Lantus mentioned above. Users also generally calculate or simply estimate the amount of insulin they need in a given dose without assistance.
However, studies have shown that a newer method, called the insulin pump, can provide a level of control beyond that achievable with standard injections. The insulin pump is a pager-sized device that contains a reservoir of insulin. A small tube connects the pump to the body. It can deliver insulin in two ways. The first, in one large dose, is used for meals and is essentially the same as the normal injection, except it is physically administered by the pump, not the user. The advantage of the pump lies in a second delivery method: a small, slow dose called a basal rate. This basal delivery more closely mirrors the action of the human pancreas, and so controls glucose levels better in the time between bolus doses. These devices usually support multiple basal rates, and the ability to compute bolus doses through a pre-programmed formula.
The prevalent form of blood glucose measurement is through a system of finger-pricking, test strips, and electronic measuring devices. A pen-like device pricks the finger of the user, allowing them to collect a small blood sample using a test strip. This strip is then inserted into a small measuring device and a reading is taken. The devices often record the results in the form of a long list, or else a log book may be used.
More sophisticated approaches to this problem are nearly available. Continuous glucose monitoring was once a cumbersome and expensive proposition, and so was only used in critical cases, such as hospitalized patients. Now, technological advances have made these devices not much larger than conventional glucose monitoring devices. The potential benefits of continuous monitoring devices are considerable. Glucose levels may fluctuate greatly between readings, and there is no way of telling this directly without continuous monitoring.
The
most common current way for a user to control an insulin pump is through a
low-res, monochrome screen, with only a few buttons, such as a directional
pad, OK, and Cancel. Some devices feature a small pager-like device that
communicates wirelessly with the pump itself, though the basic interface is
unchanged. Continuous blood sugar monitoring is possible today, but is not
common. The traditional method of finger-pricking to gain blood samples for
testing devices is still prevalent. However, building monitoring into the
pump itself appears to be a near-future reality (see Figure 1), as such
devices are already beginning to enter clinical trials. Automated glucose
control by the pump, which would essentially make it an autonomous
artificial pancreas, appears to be farther away, and is not a consideration
of our design.
While no PDA-based system with the capabilities of our design exists, other PDA-based systems for blood sugar management do exist and serve as the primary competition for our design. The recently discontinued TheraSense FreeStyle Tracker was a Palm-based hardware and software combination that supported glucose measurement and logging, as well as some viewing of charts and graphs of data. This product was similar to ours in that it incorporates glucose monitoring directly, but it is not continuous and does not interact directly with a glucose delivery system.
Academic Studies
Research has proven the advantages of both continuous glucose monitoring and the insulin delivery methods used in the insulin pump. A 2003 study by Chico, et al determined that continuous glucose monitoring systems were able to detect hypoglycemias, or episodes of low blood sugar, that went undetected in diabetics using traditional, or capillary, glucose measuring techniques. In type 1 diabetics, continuous monitoring was able to detect unrecognized hypoglycemias in 62.5% of those studied. Subjects used the same kinds of insulin delivery (Chico, 2003). This study demonstrates that continuous glucose monitoring can reveal import features that capillary glucose monitoring cannot. Our interface seeks to capitalize on this fact by making the data gathered by the continuous glucose monitor readily available and clear to the user.
Perhaps a more striking result is that achieved in a recent study about the efficacy of the insulin pump, specifically one from MiniMed corp, compared to that of multiple, daily injections. This Yale study, by Doyle, et al, found that users of the insulin pump were much more likely to achieve consistently acceptable glucose levels, as measured by the A1c hemoglobin test. Six times as many insulin pump users achieved the acceptable level than did users of Lantus, described above. This result shows the large potential that exists for improving glucose levels with the insulin pump. Our design seeks to expose this capability to the user in a simple and effective manner, further encouraging user involvement in the care process.